Electronic product reliability and environmental testing

The reliability of electronic products is an important indicator of their performance. Reliability is one of the focuses of product development producers and users. Environmental Stress Screening (Environmental StressScreening, ESS), that is, without damaging the product, select some typical environmental factors, by applying appropriate environmental stress, a certain number of time cycles and the stressed accumulation of the product potential acceleration defects exposed, eliminate early failure of the product.

Environmental test sequence ( s e q u e n c e o f t e s t s ) The sequence in which test samples are sequentially exposed to two or more test environments.  

1, the time interval between exposures do not typically produce significant effects on the test samples   

2 , each exposure is usually pre-processed and restored  

3 , usually before and after each exposure,   The last test of the previous exposure is the next   Initial detection of exposure

Controlled recovery conditions: actual test temperature ± 1 °C ( 15 °C -30 °C), 73% RH-77% RH , 86KPa-106KPa . (If the test sample is required to be dried before measurement,   Except as otherwise provided by the relevant regulations,   It should be dried for 6 h under the conditions described below . Standard drying conditions 55 ± 2 °C / <20% )

Recovery conditions : After the condition test, before the test: the test sample should be stable at the detection ambient temperature; when the sample changes after the test, the electrical parameters change rapidly, and should be restored according to the controlled recovery conditions; but when the electrical parameters change after the sample test is not fast, then Recovery was carried out under the test standard atmospheric pressure recovery conditions. Duration is in GB/T2423

Recovery procedure: Move to the recovery tank within 10 minutes after the condition test and complete the recovery within 30 minutes .

Environmental stress screening test equipment : constant temperature and humidity chamber , constant temperature and humidity test machine, thermal shock test chamber , walk-in test chamber, high and low temperature alternating heat and humidity test chamber, etc.

Climate test sequence:  

The sequence of climate tests is mainly applicable to various components.   In order to use it when required,   Generally considered low temperature,   high temperature,   There is a certain relationship between low pressure and alternating damp heat test.   And called the climate sequence. Order of these tests are as follows: a high temperature 'an alternating heat (maximum temperature of 5 5 ℃ 1st cycle test) a cryogenic' a low pressure (when required) an alternating heat (maximum temperature of 5 5 ℃ The rest of the trials are cycles ) .  

Climate test :

(1) High temperature test: Ba condition, 16h ± 0.5H ; recovery > 1H , detection;  

(2) Warm: 55 °C; one week;  

( 3 ) Low temperature: test Aa ; 2H ± 5min ;  

( 4 ) Low pressure: M condition, 15-35 °C; 1H ± 5min ; ( with electrical strength test, test in the last 5min ; recovery 1-2H) ;

Constant damp heat test :

Test time: 12 , 16 , 24H ; 2 , 4 , 10 , 21 , 56D 2. Test chamber conditions  

Winds> / s, a temperature change rate of 1m <0.5 ℃ / min (5min inside), humidity tolerance humidity ± 3% RH, water resistivity of <500 Ω .m, no condensation on the test sample; cooling chamber volume should be 5 times the volume of the sample .  

Precautions:  

1. After the temperature is stable ( <5min ), adjust the humidity to the predetermined severity level ( within 2H )  

2. The test time shall be counted from the time when the specified conditions are reached.  

3, the end of the test chamber should be transferred to normal atmospheric conditions, then the test sample was taken.   The first is to reduce the relative humidity, time <2h ( 0.5H internal humidity reached 73%-77%RH ); re-adjust the temperature, temperature change rate <1 °C / min ( within 5min ; reach the laboratory temperature within 0.5H ) . Except in special cases (such as the use of large test chambers)

Alternating heat and humidity :

1 , the severity level:  

High temperature: 40 °C; number of cycles 2 , 6 , 12 , 21 , 56 high temperature: 55 °C; number of cycles 1 , 2 , 6

2 , preparation before the start of the test (stable):  

After placing the sample in the test chamber, the temperature is raised to 25 °C ± 3K , and the sample temperature is stabilized , at which time the humidity is 45% RH-75% RH . . Humidity >95% RH , time <1H . ★ ( High humidity purpose: condensation on the surface of the test sample when lifting temperature ) ★  

3 , 12h + 12h cycle process:  

Temperature rise: 3H ± 0.5H reaches the maximum temperature, and the humidity at this stage is >95% RH .  

Temperature maintenance: test temperature ± 2 °C, to 12H at the beginning of the cycle , humidity >90% RH in the initial and last 15min of the test

4 , cooling:    

Method 1: 3-6H . The temperature drops to 25 °C ± 3K . The temperature dropped to 25 °C ± 3K within 3h ± 15min : the first 15min , and the initial 1.5H , humidity > 90% RH ; the rest of the time humidity > 95% RH (including 1.5H after the cooling process ). (Scope of application: Suitable for moisture infiltration samples caused by respiration, such as condensation on the inner surface caused by the inner surface of the inner surface)  

Method 2: There is no initial 1.5H requirement; humidity > 80% RH . (Scope of application: very reproducible)  

Temperature retention: 25 °C ± 3K ; humidity > 95% RH . One cycle ends until 24 hours.

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